The vegetation of the habitat of the Brenton blue butterfly, Orachrysops niobe (Trimen), in the Western Cape, South Africa

The Brenton blue butterfly is known only from a small population in one hectare of asteraceous coastal fynbos at Brenton-on-Sea. This fynbos is characterized by a great diversity of shrubs, herbs and graminoids, with a successional gradient to thicket where Pterocelastrus tricuspidatus is dominant. The eggs of the butterfly are laid on the lower side of the leaves of Indigofera erecta, on which the larvae feed. Fifteen 1-m² quadrats containing plants of Indigofera erecta with and without eggs of the butterfly were distinguished and sampled separately from 15 1-m² quadrats containing plants of Indigofera erecta without eggs. No marked differences in total vegetation, shrub or herb cover between the sites with and without eggs were observed. There was a difference in abundance of the fern Pteridium aquilinum, with over 30% cover at sites with no eggs and only about 6% at sites with eggs present. This could reflect the absence of other plants where the ferns had such dense cover

Regeneration of grassy fynbos near Grahamstown (eastern Cape) after fire

The regeneration of grassy fynbos was studied for a period of 13months after the original vegetation had been totally destroyed by fire. Because the fire was preceded by a very dry spell and succeeded by months of high rainfall, regeneration proved to be rapid and the growth of some of the species was clearly related to rainfall. Species recolonization was very rapid and in a particular order. The classification of the species into regeneration type and phenological groups relates well to other studies on fire regeneration in the fynbos. After 13months over 100 species had returned to the area, the plants showing a progressive increase in height, basal and aerial cover

Multiple Deprivation, Severity and Latent Sub-Groups:Advantages of Factor Mixture Modelling for Analysing Material Deprivation

Material deprivation is represented in different forms and manifestations. Two individuals with the same deprivation score (i.e. number of deprivations), for instance, are likely to be unable to afford or access entirely or partially different sets of goods and services, while one individual may fail to purchase clothes and consumer durables and another one may lack access to healthcare and be deprived of adequate housing . As such, the number of possible patterns or combinations of multiple deprivation become increasingly complex for a higher number of indicators. Given this difficulty, there is interest in poverty research in understanding multiple deprivation, as this analysis might lead to the identification of meaningful population sub-groups that could be the subjects of specific policies. This article applies a factor mixture model (FMM) to a real dataset and discusses its conceptual and empirical advantages and disadvantages with respect to other methods that have been used in poverty research . The exercise suggests that FMM is based on more sensible assumptions (i.e. deprivation covary within each class), provides valuable information with which to understand multiple deprivation and is useful to understand severity of deprivation and the additive properties of deprivation indicators

From Each According to His Surplus: Equi-Proportionate Sharing of Commodity Tax Burdens

This paper examines the incidence of commodity taxes, finding that, when demand and marginal cost schedules are linear. the burden of commodity taxation is distributed between buyers and sellers so that each suffers the same percentage reduction on pre-tax surplus. This equiproportionate reduction in surplus is the outcome of commodity taxes set at any rate, and is unaffected by relative demand and supply elasticities. Hence, when demand and marginal cost schedules are linear, commodity taxes resemble flat-rate taxes imposed on market surplus. Similar results apply to nonlinear schedules with certain ranges.

Genetics of callous-unemotional behavior in children

Callous-unemotional behavior (CU) is currently under consideration as a subtyping index for conduct disorder diagnosis. Twin studies routinely estimate the heritability of CU as greater than 50%. It is now possible to estimate genetic influence using DNA alone from samples of unrelated individuals, not relying on the assumptions of the twin method. Here we use this new DNA method (implemented in a software package called Genome-wide Complex Trait Analysis, GCTA) for the first time to estimate genetic influence on CU. We also report the first genome-wide association (GWA) study of CU as a quantitative trait. We compare these DNA results to those from twin analyses using the same measure and the same community sample of 2,930 children rated by their teachers at ages 7, 9 and 12. GCTA estimates of heritability were near zero, even though twin analysis of CU in this sample confirmed the high heritability of CU reported in the literature, and even though GCTA estimates of heritability were substantial for cognitive and anthropological traits in this sample. No significant associations were found in GWA analysis, which, like GCTA, only detects additive effects of common DNA variants. The phrase ‘missing heritability’ was coined to refer to the gap between variance associated with DNA variants identified in GWA studies versus twin study heritability. However, GCTA heritability, not twin study heritability, is the ceiling for GWA studies because both GCTA and GWA are limited to the overall additive effects of common DNA variants, whereas twin studies are not. This GCTA ceiling is very low for CU in our study, despite its high twin study heritability estimate. The gap between GCTA and twin study heritabilities will make it challenging to identify genes responsible for the heritability of CU

Dense-core senile plaques in the Flemish variant of Alzheimer's disease are vasocentric

Alzheimer's disease (AD) is characterized by deposition of beta-amyloid (Abeta) in diffuse and senile plaques, and variably in vessels. Mutations in the Abeta-encoding region of the amyloid precursor protein (APP) gene are frequently associated with very severe forms of vascular Abeta deposition, sometimes also accompanied by AD pathology. We earlier described a Flemish APP (A692G) mutation causing a form of early-onset AD with a prominent cerebral amyloid angiopathy and unusually large senile plaque cores. The pathogenic basis of Flemish AD is unknown. By image and mass spectrometric Abeta analyses, we demonstrated that in contrast to other familial AD cases with predominant brain Abeta42, Flemish AD patients predominantly deposit Abeta40. On serial histological section analysis we further showed that the neuritic senile plaques in APP692 brains were centered on vessels. Of a total of 2400 senile plaque cores studied from various brain regions from three patients, 68% enclosed a vessel, whereas the remainder were associated with vascular walls. These observations were confirmed by electron

Latent class analysis of the Child Behavior Checklist Obsessive-Compulsive Scale

The Obsessive-Compulsive Scale (OCS) of the Child Behavior Checklist (CBCL) predicts obsessive-compulsive disorder and is highly heritable. Latent class analysis (LCA) of the OCS was used to identify profiles within this 8-item scale and to examine heritability of those profiles. The LCA was performed on maternal CBCL reports of their 6- to 18-year-old children from 2 US nationally representative samples from 1989 (n = 2475, 50% male) and 1999 (n = 2029, 53% male) and from Dutch twins in the Netherlands Twin Registry at ages 7 (n = 10 194, 49.3% male), 10 (n = 6448, 48.1% male), and 12 (n = 3674, 48.6% male) years. The heritability of the resultant classes was estimated using odds ratios of twin membership across classes. A 4-class solution fitted all samples best. The resulting classes were a "No or Few Symptoms" class, a "Worries and Has to Be Perfect" class, a "Thought Problems" class, and an "OCS" class. Within-class odds ratios were higher than across-class odds ratios and were higher for monozygotic than dizygotic twins. We conclude that LCA identifies an OCS class and that class is highly heritable using across-twin comparisons. © 2009 Elsevier Inc. All rights reserved

Simultaneous Determination of Various Isothiocyanates by RP-LC Following Precolumn Derivatization with Mercaptoethanol

Numerous isothiocyanates (ITCs) are poorly soluble in water which causes their precipitation in aqueous mobile phases used in reversed phase liquid chromatography (RP-LC), thus impacting the accuracy of the quantification. By comparing the amounts of ITCs injected and released from the column, losses could be estimated at 5–32% depending on polarities and concentrations. Results could be dramatically improved in terms of separation and quantification using RP-LC with a mercaptoethanol precolumn derivatization aimed at avoiding ITCs precipitation. The cancer chemoprotective allyl-ITC and sulforaphane were found in cabbage extracts at 1.2 and 2.7 μg g−1 fresh weight, respectively